Apparatus for obtaining substantially uniform irradiation from a nonuni form source



Feb. 16, 1960 c. M. 'ZOUBEK .9

APPARATUS FOR'OBTAINING SUBSTANTIALLY UNIFORM IRRADIATION FROM A NONUNIFORM SOURCE Filed Oct. 20, 1954 um u 'ug n u mmvrm CHAPL 5 M ZOUBEK ATTORNEY practical: purposes this can: befapproximatedb j a: r I v cosine curve. A line of movement of the product 2,925,496 through the beam isvchosenand parts of the area of'the a r beama're shadowed with the shadowing being such that f as FORM SOURCE I along lines parallel to the path vof travel through e 7 t H beamfare inversely proportional to the average intensity ar lfi Oak wms l-a si q W along the line or each dimension. m the case'of an Company Chlcaglb -t a lf o of m m electron beam having afdistribution "corresponding to: a

- Application October '20,"1"954, Serial No. 463,510" eheb y curve; h ng 1 these dimensions f,

r n the unshaded arealasjm easured along linesparallel to the 4 Claims- 2 pathiof movement vary as-a probability curve with the i e shortest dimension,intersectingtheaxis of the beam and t. l; I the longer dimension spaced to each side thereof; I

The Present ent on rel s o me hod and PP "Referring to- Figured, an electron tube generally 10' tus for obtaining substantially uniform dosage in the h wi dow 11 from which'a cathode ray beam 12 is irradiation of product from. a nonuniform source, as for emitted; Such an electron generator is conventionaland example a beam of electrons from a cathode ray tube. f m' part of the present inventio -t on v yp is e:

With the usual cathode ray tube Operating at r la e y scribed in the article Radiation Sterilization III by J. high powers, there is an inherent focusing of the electrons A, K lton, G. R. Mahn and J; W. Rantfl,-'pub lished emitted from the window at the end of the tube. Thi in Nucleonics, volume 11, Number l1, 'dat'ed November produces a beam of electrons that has a core, in which 1953, atpages 64 et'seq, The productsto be irradiated the electrons are ly concentrated, Surrounded y areas, in theillustrated embodiment are a plurality of units -14 f increasingly l d ity-V. W h a beam is u which are passedlthrough the beam'in a .given direction irr di t Product,.thea1'.eas. of hig nc n ra on at "a' uniform'rate of speed by a belt conveyor 15. 'A Obviously receive a h heavier dosage than do the shield .16 is positioned between the window 11 and the areas where there is a lesser concentration of electrons. product 14 to shadow portions of the area traversed. by Various expedients v been. tried i l rthe units of product 14. The'shield has a cutout 17 to obtain a more uniform beam. Oneofethese has: been id u hadqwed areas. The cutout is shaped so' to p the beam through something thatwould d fi eao that-fall of the dimensions asmeasured parallel to the e it'SO as it) scatter the electrons .an dvthusproduce 3 more '7 path of travel f the product along conveyor 15 vary even eoncentration throughout" the area coveredbylthe i h at re f a probability curve (or for most vpur- I ibea'l n. Anot el expedient h been lto'rl'apidly w poses a cosine'curve'willsufiicey-j"In the illustrated emthe beam back and forth much in themannerimwhich bbdi-mem hi i ehieved .by having'thetwo opposite a beam of'electrons is swept across vthe face of a oath d 13 a d'lg f theicutp'bl-rlltgf-vwhibhiiwonedges a e Ode y tube in a television w high energy e transverse'to the-pathof movement, shaped in the form, trons this requires substantial amounts of power. "It also of i i jurves I I I e is somewhat difficult to obtain a sweeping ratethat wlll In a e im mm f uselwith an Produce relatively uniform dosages throughout 'the'area: electron generator having a peak output of 800,000 eleccovered. V 1 r40 tronf'volts, the shield was made of one-eighth inch alu- The Principal Object of t Present inventlon is to P minum sheet. 'The distance between the two. peaks of Vide a relatively Simple methed d PP ratus for Oh the edges 18 and 19,'which-dimensionwas positioned taining such uniform dosages. In most installations the to intersct h i of h b was three and fi et a only additional piece of equipment required is a shield sixtegmhs inches h edges 13 and 19 are out to that is simple to make and which does not requ re'repalr 5 respond to-pmbability g v amquntmof the d r and replacement. A conveyor ls also used, but normally i curve employed s that a'tthe s e. Y this conveyor would be reqmredanyhow because of axis dimension of the c'urve.,was ten percent .of-the maxidanger in permitting employ to be around the area mum'Y axis dimension at centerof the curve. i The e I uct past the window of the tube for'irradiationi Such J from the/following description taken in'conjunotion- 'with 'an apparatus embodying the present invention, and

l of Figure '1. V

to determine the variationsin intensity ofthe -concentra a from theelectron window; "'If other sou'rcesiofirradi j :ation are used a similar. procedure is followed. 'In'most it probability curve centered about' the axis of, th

ered by'a cathode ray tube when it is operating Con- I I tinued exposure to the electrons and to theX- raystproz i gi f i F g ;z

duced by the. electrons striking various substancescan; Vie l e e A P s11 1 Be r 1 7 7 trom the product. The maximum width of the cut out be dangerous. As a result, where there is'any amoufntf a l V 1 of operation at all a conveyor is used tocarry'the prod: W a -F maxmlum e thtai ee uredg parallel to thellne'tof-movement'was seven inches.

the invention. g 1 l w v t v v. 7

Other objects and advantages willibecor'ne apparent product was three and oneeeighthjnches. v i

a ln-another embodinientthe hield was positioned one the drawings, in which: 4 m a a I p V w Fhalf -inch .above} the productlandeight inches; from"'the-f 1'. Figure l is a schematicelevational view'of a part-of i d 11;; Th? i ncgf em e M P k' 'J {ledges 18andf1 9 was fol ir and three-quarters'inches, while I he maximumlwidth of ethef cut' out iwasfsevenand five: a V ighths'inicih eSQ The maximumlength oftheleut out par;- -'alle1 to theline offmovemfent was twelve an'ti thr ee quarters inchesan'd the maximumxwid-th of theproduct a conveyor continually'operated is, utilized asja part of wi e e p he nax muln' itlie 4- I -as'measuredxtransversejothepath of mover'nent"of'the 1- Figure 2 is a schematic plan view l taken atline The method for obtaining'fthesubstantially on an; coverage in accordance with the present inventionis first 5 tion of the electrons in a given area in a' lane s'acedg "wa and e rt m es a ,t ,p, ,P l V p "-The] foregoing'description of 'a' specificl'embodilrient is for thej purpose 0f compliancewith 35 iU;S;C. "ll2;1and liloInotjdes'ire tobelimited tci the, exactrdetail's shown l andf5described, folfobv'ious rnodifications will" occur to electron irradiation equipment it will be found thafi the distribution of the electrons in thebe'am is that-of a I claim:

tvveen said path and said 1. A device for obtaining subst antially uniform cover age in the irradiation of afproduct, said device including a nonuniform source of irradiation, means for mov ing said product along a given path-in a given direction through an area subjected to a beam of irradiation from said source, and a mask interposed between said path and said source, said mask having an opening therein positioned in said beam, the dimensions of the opening, as measured along lines parallel to said path, being inversely proportional to the average intensity of irradiation along said lines, v s

I 2. A device forobtaining substantially uniform coverage in the irradiation of a product from a nonuniform sourceof irradiation, said device including means for moving said product along a given path in a given direction through an area, subjected to a beam of irradiation from said source, and a mask interposed between said path and said source, said mask having an opening therein positioned in said beam, the dimensions of the open! ing, as measured along lines parallel to saidpath, being inversely proportional to the average intensity of irradiation along said lines.

3. A device for obtaining substantially uniform coverage in the irradiation, from a nonuniform source, of a product moving along a given path in a given direction through an area subjected to a beamof irradiation from said source, said device including a mask interposed besource, said mask having an opening therein positioned in said beam, the dimensions of the opening, asmeasuredalong lines parallel to said path, being inversely proportional to the average intensity of irradiation along said lines.

4. A device for obtaining substantiantially uniform coverage in the irradiation by an electron gun of a product moving along; a given path in;a given direction through an area of irradiation from said. gun, said device including a mask interposed between said path and said gun, said mask havingan opening therein positioned about the axisof irradiation from said gun Iwith the dimensions of the opening, as measured along lines parallel to said path, varying in accordance with a probability curve with the shortest'dimension intersecting the axis of the irradiation from said gun.

References Cited in thefile of this patent UNITED STATES PATENTS 1,535,359 Tousey Apr. 28, 1925 2,313,018 Krause Mar. 2, 1943 2,347,982 Bachman May 2, 1944 2,489,172 Brandt Nov. 22, 1949 2,630,536 Uladeff Mar. 3, 1953 2,675,485 Scag Apr. 13, 1954' 2,722,620 Gale Nov. 1, 1955 2,724,059 Gale Nov. 15, 1955 2,746,193 Billian May 22, 1956 

